Patent Application
20200138327
The present invention relates to a biometric antenna device, and more particularly to a biometric antenna device that emits radio waves toward a measurement site of a living body or receives radio waves from the measurement site for measurement of biological information. In addition, the present invention relates to a pulse wave measurement device, a blood pressure measurement device, and an apparatus including the biometric antenna device. In addition, the present invention relates to a biological information measurement method for emitting radio waves toward a measurement site of a living body or receiving radio waves from the measurement site. In addition, the present invention relates to a pulse wave measurement method and a blood pressure measurement method including the biological information measurement method.
Conventionally, as this kind of biometric antenna device, for example, as disclosed in Patent Document 1 (Japanese Patent No. 5879407), a biometric antenna device is known that includes a transmitting (emitting) antenna and a receiving antenna facing a measurement site, that emits a radio wave (measurement signal) from the transmitting antenna toward the measurement site (target object), that receives a radio wave reflected by this measurement site (reflected signal) by the receiving antenna, and that measures biological information.
However, in Patent Document 1, there is no disclosure or suggestion how to arrange the transmitting antenna and the receiving antenna (appropriately, these are collectively referred to as “transmitting and receiving antenna pair”) at a predetermined distance with respect to the measurement site. For example, when the measurement site is the wrist, if the distance between the outer surface of the wrist and the transmitting and receiving antenna pair varies with each measurement, the received signal level varies, and there arises a problem that biological information cannot be measured with high precision.
Thus, an object of the present invention is to provide a biometric antenna device capable of keeping a conductor layer forming a transmitting and receiving antenna pair at a predetermined distance with respect to a measurement site, and therefore capable of measuring biological information from the measurement site with high precision. In addition, an object of the present invention is to provide a pulse wave measurement device, a blood pressure measurement device, and an apparatus including the biometric antenna device. In addition, an object of the present invention is to provide a biological information measurement method for measuring biological information from a measurement site using the biometric antenna device. In addition, the present invention is to provide a pulse wave measurement method and a blood pressure measurement method including the biological information measurement method.
In order to solve the above-mentioned problem, a biometric antenna device of the present invention for emitting a radio wave toward a measurement site of a living body or for receiving a radio wave from the measurement site, the biometric antenna device comprises:
a conductor layer configured to face the measurement site for emitting and/or receiving the radio wave; and
a dielectric layer mounted along a facing surface facing the measurement site of the conductor layer or of a base material mounting the conductor layer and extending in parallel with the conductor layer, the dielectric layer having a predetermined relative permittivity,
wherein the dielectric layer keeps a distance between an outer surface of the measurement site and the conductor layer constant, in a mounted state in which a second surface on a side opposite to a side of a first surface on a side along the conductor layer of the dielectric layer abuts on an outer surface of the measurement site.
In the present specification, the “measurement site” may be a trunk in addition to a rod-shaped site such as an upper limb (wrist, upper arm, or the like) or a lower limb (ankle, or the like).
In addition, the “outer surface” of the measurement site refers to a surface exposed to the outside. For example, if the measurement site is a wrist, it refers to the outer peripheral surface of the wrist or a part thereof (for example, the palmar surface corresponding to the palmar side portion in the circumferential direction of the outer peripheral surface).
In addition, the “conductor layer” can be used, for emitting and/or receiving a radio wave, as a transmitting antenna or a receiving antenna, or as a transmitting and receiving shared antenna via a known circulator. The “conductor layer” may be divided into a transmitting antenna and a receiving antenna that receives a radio wave from the transmitting antenna.
In addition, unless otherwise noted, the “predetermined relative permittivity” of the dielectric layer may be uniform over the range in which the dielectric layer occupies space, or may vary depending on the position within a range in which the dielectric layer occupies space.
In addition, a phrase that the dielectric layer “keeps a distance constant” between an outer surface of the measurement site and the conductor layer means that the dielectric layer is a spacer. It should be noted that in the case where the dielectric layer has flexibility, it means acceptable that the “distance” more or less fluctuates due to the bending when it is bent by an external force.
In another aspect, a pulse wave measurement device of the present disclosure for measuring a pulse wave of a measurement site of a living body, the pulse wave measurement device comprises:
the biometric antenna device;
wherein the second surface of the dielectric layer is configured to abut on an outer surface of the measurement site, and a transmitting and receiving antenna pair including a transmitting antenna and a receiving antenna formed by the conductor layer is configured to correspond to an artery passing through the measurement site in a mounted state in which the belt is mounted to wind around an outer surface of the measurement site,
a transmitting circuit configured to emit a radio wave toward the measurement site via the transmitting antenna;
a receiving circuit configured to receive a radio wave reflected by the measurement site via the receiving antenna; and
a pulse wave detection unit configured to acquire a pulse wave signal representing a pulse wave of an artery passing through the measurement site based on an output of the receiving circuit.
Here, when the conductor layer is divided into a transmitting antenna and a receiving antenna that receives a radio wave from the transmitting antenna in the surface direction perpendicular to the thickness direction of the conductor layer, the “transmitting and receiving antenna pair” refers to the transmitting antenna and the receiving antenna. In addition, when the conductor layer spatially forms one transmitting and receiving shared antenna, all of the “transmitting antenna”, the “receiving antenna”, and the “transmitting and receiving antenna pair” refer to the transmitting and receiving shared antenna.
In another aspect, a blood pressure measurement device of the present disclosure for measuring blood pressure of a measurement site of a living body, the blood pressure measurement device comprises:
the two sets of pulse wave measurement devices;
wherein a belt in the two sets is integrally formed,
wherein transmitting and receiving antenna pairs in the two sets are arranged apart from each other in a width direction of the belt,
wherein in a mounted state where the belt is mounted to wind around an outer surface of the measurement site, the second surface of the dielectric layer abuts on an outer surface of the measurement site, and a first set of transmitting and receiving antenna pair of the two sets corresponds to an upstream side portion of an artery passing through the measurement site, while a second set of transmitting and receiving antenna pair corresponds to a downstream side portion of the artery,
wherein in each of the two sets, the transmitting circuit emits a radio wave toward the measurement site via the transmitting antenna, and the receiving circuit receives a radio wave reflected by the measurement site via the receiving antenna, and
wherein in each of the two sets, the pulse wave detection unit acquires a pulse wave signal representing a pulse wave of an artery passing through the measurement site based on an output of the receiving circuit,
a time difference acquisition unit configured to acquire a time difference between pulse wave signals acquired by the two sets of respective pulse wave detection units as a pulse transit time; and
a first blood pressure calculation unit configured to calculate a blood pressure value based on a pulse transit time acquired by the time difference acquisition unit by using a predetermined correspondence formula between a pulse transit time and a blood pressure.
In another aspect, an apparatus of the present disclosure comprises:
the biometric antenna device;
the pulse wave measurement device; or
the blood pressure measurement device.
In another aspect, a biological information measurement method of the present disclosure for acquiring biological information from a measurement site of a living body by using the biometric antenna device, the biological information measurement method comprises:
causing the second surface of the dielectric layer to abut on an outer surface of the measurement site to mount the biometric antenna device on the measurement site; and
in a mounted state where the dielectric layer keeps a distance between an outer surface of the measurement site and the conductor layer constant, emitting a radio wave from the conductor layer toward the measurement site through the dielectric layer or a gap present on a side of the dielectric layer, and/or receiving a radio wave reflected by the measurement site with the conductor layer through the dielectric layer or a gap present on a side of the dielectric layer.
In another aspect, a pulse wave measurement method of the present disclosure for measuring a pulse wave of a measurement site of a living body by using the pulse wave measurement device, the pulse wave measurement method comprises:
mounting the belt to wind around an outer surface of the measurement site, causing the second surface of the dielectric layer to abut on an outer surface of the measurement site, and causing a transmitting and receiving antenna pair including a transmitting antenna and a receiving antenna formed by the conductor layer to correspond to an artery passing through the measurement site;
in a mounted state in which the dielectric layer keeps a distance between the measurement site and the conductor layer constant, emitting a radio wave toward the measurement site with the transmitting circuit via the transmitting antenna, and receiving a radio wave reflected by the measurement site with the receiving circuit via the receiving antenna; and
acquiring a pulse wave signal representing a pulse wave of an artery passing through the measurement site with the pulse wave detecting unit based on an output of the receiving circuit.
In another aspect, a blood pressure measurement method of the present disclosure for measuring blood pressure of a measurement site of a living body by using the blood pressure measurement device, the blood pressure measurement method comprises:
mounting the belt to wind around an outer surface of the measurement site, causing the second surface of the dielectric layer to abut on an outer surface of the measurement site, and causing a first set of transmitting and receiving antenna pair of the two sets to correspond to an upstream side portion of an artery passing through the measurement site, while causing a second set of transmitting and receiving antenna pair to correspond to a downstream side portion of the artery;
in a mounted state where the dielectric layer keeps a distance between the measurement site and the conductor layer constant, in each of the two sets, emitting a radio wave toward the measurement site with the transmitting circuit via the transmitting antenna, and receiving a radio wave reflected by the measurement site with the receiving circuit via the receiving antenna;
in each of the two sets, acquiring a pulse wave signal representing a pulse wave of an artery passing through the measurement site with the pulse wave detection unit based on an output of the receiving circuit;
acquiring a time difference between pulse wave signals acquired by the two sets of respective pulse wave detection units with the time difference acquisition unit as a pulse transit time; and
calculating a blood pressure value with the first blood pressure calculation unit based on a pulse transit time acquired by the time difference acquisition unit by using a predetermined correspondence formula between a pulse transit time and a blood pressure.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Configuration of Sphygmomanometer)
As illustrated in these drawings, the sphygmomanometer 1 broadly includes a belt 20 to be mounted around a user's left wrist 90 and a main body 10 integrally attached to the belt 20.
As understood from
The main body 10 is integrally provided at one end portion 20e of the belt 20 in the circumferential direction by integral molding in this example. It should be noted that the belt 20 and the main body 10 may be separately formed, and the main body 10 may be integrally attached to the belt 20 via an engaging member (for example, a hinge or the like). In this example, the site where the main body 10 is disposed is intended to correspond to the back side surface of the left wrist 90 (the surface on the back side of the hand) 90b in the mounted state (see
As understood from
A display 50 serving as a display screen is provided on the top surface 10a of the main body 10 (the surface on a side farthest from the measurement site). In addition, an operation unit 52 for inputting instructions from the user is provided along the side surface 10f of the main body 10 (side surface on the left front side in
A transmission and reception unit 40 constituting first and second pulse wave sensors is provided in a site between one end portion 20e and the other end portion 20f in the circumferential direction of the belt 20. Of the belt 20, on the inner peripheral surface 20a of the site where the transmission and reception unit 40 is disposed, four transmitting and receiving antennas 41 to 44 (all of which are referred to as “transmitting and receiving antenna group” and denoted by reference numeral 40E) are mounted in a state of being separated from each other in the width direction Y of the belt 20 (described in detail below). In this example, the site where the transmitting and receiving antenna group 40E is disposed in the longitudinal direction X of the belt 20 is intended to correspond to the radial artery 91 of the left wrist 90 in the mounted state (see
As illustrated in
When mounting the sphygmomanometer 1 on the left wrist 90, the user inserts the left hand into the belt 20 in the direction indicated by the arrow A in
As illustrated in
In this example, as illustrated in
In this example, one transmitting antenna or receiving antenna has a square shape of 3 mm both in length and width (this shape in the surface direction is referred to as a “pattern shape”) in the surface direction (meaning the direction along the outer peripheral surface of the left wrist 90 in
In addition, as shown in
In this example, the conductor layer 401 is made of metal (for example, copper). In this example, the dielectric layer 402 is made of polycarbonate, so that the relative permittivity of the dielectric layer 402 is uniformly set to εr≈3.0. It should be noted that the relative permittivity means a relative permittivity at a frequency of 24 GHz band of radio waves used for transmission and reception (the same applies hereinafter).
This transmitting and receiving antenna group 40E can be configured to be flat along the surface direction u along the outer peripheral surface of the left wrist 90. Therefore, in the sphygmomanometer 1, the belt 20 can be configured to be thin as a whole. In this example, the thickness of the conductor layer 401 is set to h1=30 μm, and the thickness of the dielectric layer 402 is set to h2=2 mm.
The display 50 includes an organic electro luminescence (EL) display in this example, and displays information related to blood pressure measurement such as blood pressure measurement results and other information in accordance with a control signal from the CPU 100. It should be noted that the display 50 is not limited to the organic EL display, and may include another type of display such as a liquid crystal display (LCD).
The operation unit 52 includes a push switch in this example, and inputs an operation signal corresponding to the user's instructions to start or stop blood pressure measurement into the CPU 100. It should be noted that the operation unit 52 is not limited to the push switch, and may be, for example, a pressure-sensitive (resistive) or proximity (capacitive) touch panel switch. In addition, the operation unit 52 may include a microphone (not shown) to input a blood pressure measurement start instructions in response to the user's voice.
The memory 51 non-transitorily stores data of a program for controlling the sphygmomanometer 1, data used for controlling the sphygmomanometer 1, setting data for setting various functions of the sphygmomanometer 1, data of measurement results of blood pressure values, and the like. In addition, the memory 51 is used as a work memory or the like when a program is executed.
The CPU 100 executes various functions as a control unit in accordance with a program for controlling the sphygmomanometer 1 stored in the memory 51. For example, when blood pressure measurement is performed by the oscillometric method, the CPU 100 performs control to drive the pump 32 (and the valve 33) based on a signal from the pressure sensor 31 in response to instructions to start blood pressure measurement from the operation unit 52. In addition, the CPU 100 performs control to calculate the blood pressure value based on the signal from the pressure sensor 31 in this example.
The communication unit 59 is controlled by the CPU 100 to transmit predetermined information to an external device via the network 900, receive information from an external device via the network 900, and to deliver the information to the CPU 100. The communication via the network 900 may be wireless or wired. In this embodiment, the network 900 is the Internet, but is not limited thereto, and may be another type of network such as a hospital local area network (LAN), or may be one-to-one communication using a USB cable or the like. The communication unit 59 may include a micro USB connector.
The pump 32 and the valve 33 are connected to the pressing cuff 21 via the air pipe 39, and the pressure sensor 31 is connected to the pressing cuff 21 via the air pipe 38. It should be noted that the air pipes 39 and 38 may be one common pipe. The pressure sensor 31 detects the pressure in the pressing cuff 21 via the air pipe 38. The pump 32 includes a piezoelectric pump in this example and supplies air as a fluid for pressurization to the pressing cuff 21 through the air pipe 39 in order to raise the pressure in the pressing cuff 21 (cuff pressure). The valve 33 is mounted on the pump 32, and is configured to be controlled in opening/closing as the pump 32 is turned on/off. That is, when the pump 32 is turned on, the valve 33 closes and air is filled into the pressing cuff 21, while when the pump 32 is turned off, the valve 33 opens and the air in the pressing cuff 21 is discharged into the atmosphere through the air pipe 39. It should be noted that the valve 33 has a function of a check valve so that the discharged air does not flow back. The pump drive circuit 320 drives the pump 32 based on a control signal supplied from the CPU 100.
The pressure sensor 31 is a piezoresistive pressure sensor in this example, and detects the pressure of the belt 20 (pressing cuff 21), a pressure with the atmospheric pressure as a reference (zero) in this example, through the air pipe 38 to output the detected result as a time-series signal. The oscillation circuit 310 oscillates based on an electrical signal value based on a change in electrical resistance due to the piezoresistive effect from the pressure sensor 31, and outputs a frequency signal having a frequency corresponding to the electrical signal value of the pressure sensor 31 to the CPU 100. In this example, the output of pressure sensor 31 is used for controlling the pressure of the pressing cuff 21, and for calculating the blood pressure value (including systolic blood pressure (SBP) and diastolic blood pressure (DBP)) by the oscillometric method.
The battery 53 supplies power to elements mounted on the main body 10, in this example, to each element of the CPU 100, the pressure sensor 31, the pump 32, the valve 33, the display 50, the memory 51, the communication unit 59, the oscillation circuit 310, and the pump drive circuit 320. In addition, the battery 53 also supplies power to the transmitting and receiving circuit group 45 of the transmission and reception unit 40 through the wiring line 71. This wiring line 71 is provided to extend between the main body 10 and the transmission and reception unit 40 along the longitudinal direction X of the belt 20 in a state of being sandwiched between the strip 23 and the pressing cuff 21 of the belt 20 together with the signal wiring line 72.
The transmitting and receiving circuit group 45 of the transmission and reception unit 40 includes transmitting circuits 46 and 49 connected to the transmitting antennas 41 and 44, respectively, and receiving circuits 47 and 48 connected to the receiving antennas 42 and 43, respectively. As shown in
As described in detail below, the pulse wave detection units 101 and 102 shown in
In the mounted state, as shown in
In this example, the reception levels of the receiving antennas 42 and 43 are about 1 μW (−30 dBm in decibel value with reference to 1 mW). The output levels of the receiving circuits 47 and 48 are about 1 volt. In addition, the respective peaks A1 and A2 of the first pulse wave signal PS1 and the second pulse wave signal PS2 are approximately 100 mV to 1 volt.
It should be noted that assuming that the pulse wave velocity (PWV) of the blood flow of the radial artery 91 is in the range of 1000 cm/s to 2000 cm/s, since the substantial space D between the first pulse wave sensor 40-1 and the second pulse wave sensor 40-2 is 20 mm, the time difference Δt between the first pulse wave signal PS1 and the second pulse wave signal PS2 is in the range of 1.0 ms to 2.0 ms.
In the above example, the case is described where there are two sets of transmitting and receiving antenna pairs, but three or more sets of transmitting and receiving antenna pairs may be used.
(Configuration and Operation of Blood Pressure Measurement by the Oscillometric Method)
In this block configuration, roughly, a pressure control unit 201, a second blood pressure calculation unit 204, and an output unit 205 are mounted.
The pressure control unit 201 further includes a pressure detection unit 202 and a pump drive unit 203. The pressure detection unit 202 processes the frequency signal input from the pressure sensor 31 through the oscillation circuit 310, and performs processing for detecting the pressure in the pressing cuff 21 (cuff pressure). The pump drive unit 203 performs processing for driving the pump 32 and the valve 33 through the pump drive circuit 320 based on the detected cuff pressure Pc (see
The second blood pressure calculation unit 204 acquires the fluctuation component of the arterial volume included in the cuff pressure Pc as a pulse wave signal Pm (see
The output unit 205 performs processing for displaying the calculated blood pressure values (systolic blood pressure SBP and diastolic blood pressure DBP) on the display 50 in this example.
When the user instructs blood pressure measurement by oscillometric method with the push switch as the operation unit 52 provided in the main body 10 (step S1), the CPU 100 starts operation to initialize the processing memory area (step S2). In addition, the CPU 100 turns off the pump 32 via the pump drive circuit 320, opens the valve 33, and discharges the air in the pressing cuff 21. Subsequently, control is performed to set the current output value of the pressure sensor 31 as a value corresponding to the atmospheric pressure (0 mmHg adjustment).
Subsequently, the CPU 100 operates as the pump drive unit 203 of the pressure control unit 201 to close the valve 33, and then drives the pump 32 via the pump drive circuit 320 to perform control to send air to the pressing cuff 21. Thus, the pressing cuff 21 is inflated and the cuff pressure Pc (see
In this pressurization process, in order to calculate the blood pressure value, the CPU 100 works as the pressure detection unit 202 of the pressure control unit 201, monitors the cuff pressure Pc with the pressure sensor 31, and acquires, as a pulse wave signal Pm as illustrated in
Next, in step S4 in
At this time, if the blood pressure value cannot be calculated yet because of insufficient data (NO in step S5), unless the cuff pressure Pc reaches the upper limit pressure (for safety, for example, 300 mmHg is predetermined), the processing of steps S3 to S5 is repeated.
If the blood pressure value can be calculated in this manner (YES in step S5), the CPU 100 stops the pump 32, opens the valve 33, and performs control to discharge the air in the pressing cuff 21 (step S6). Then, lastly, the CPU 100 works as the output unit 205, displays the measurement result of the blood pressure value on the display 50, and records the measurement result in the memory 51 (step S7).
It should be noted that the calculation of the blood pressure value may be performed not only in the pressurization process, but also in the depressurization process.
(Operation of Blood Pressure Measurement Based on Pulse Transit Time)
When the user gives an instruction to perform the PTT-based blood pressure measurement with a push switch as the operation unit 52 provided on the main body 10, the CPU 100 starts operation. That is, the CPU 100 closes the valve 33 and drives the pump 32 via the pump drive circuit 320, and performs control to send air to the pressing cuff 21 to expand the pressing cuff 21 and to increase the cuff pressure Pc (see
At this time, as shown in
Next, in the mounted state, as shown in step S12 in
Next, as shown in step S13 in
Next, as shown in step S14 in
Thereafter, as shown in step S15 in
EBP=α/DT
2+β (Eq. 1)
(where each of α and β represents a known coefficient or constant) (see, for example, JP H10-201724 A).
It should be noted that as a predetermined correspondence formula Eq between pulse transit time and blood pressure, another known correspondence formula such as a formula including the term of 1/DT and the term of DT may be used in addition to the term of 1/DT2, such as shown in another formula:
EBP=α/DT
2
+β/DT+γDT+δ (Eq. 2)
(where each of α, β, γ, and δ represents a known coefficient or constant).
When the blood pressure is calculated (estimated) in this way, as described above, in each of the first pulse wave sensor 40-1 and the second pulse wave sensor 40-2, the dielectric layer 402 keeps the distance between the palmar surface 90a of the left wrist 90 and the conductor layer 401 constant. In addition, due to the dielectric layer 402 interposed between the palmar surface 90a of the left wrist 90 and the conductor layer 401, it is less likely to be affected by fluctuations in the dielectric constant of the living body (the relative permittivity of the living body varies in the range of about 5 to 40). In addition, since room between the palmar surface 90a of the left wrist 90 and the conductor layer 401 can be made, the range (area) irradiated with radio waves on the palmar surface 90a of the left wrist 90 can be expanded as compared with the case where the conductor layer 401 is in direct contact with the palmar surface 90a of the left wrist 90. Therefore, even if the mounting position of the conductor layer 401 is slightly shifted from directly above the radial artery 91, the signal reflected by the radial artery 91 can be stably received. As a result, the signal levels received by the respective receiving circuits 47 and 48 are stabilized, and the pulse wave signals PS1 and PS2 as biological information can be acquired with high precision. As a result, the pulse transit time (PTT) can be acquired with high precision, and therefore, the blood pressure value can be calculated (estimated) with high precision. It should be noted that the measurement result of the blood pressure value is displayed on the display 50 and recorded in the memory 51.
In this example, if measurement stop is not instructed by the push switch as the operation unit 52 in step S16 in
According to the sphygmomanometer 1, the blood pressure measurement based on the pulse transit time (PTT) allows blood pressure to be measured continuously over a long period of time with a reduced physical burden on the user.
In addition, according to the sphygmomanometer 1, the blood pressure measurement (estimation) based on pulse transit time and the blood pressure measurement by the oscillometric method can be performed using a common belt 20 with an integrated device. Therefore, the convenience of the user can be enhanced. For example, in general, when blood pressure measurement (estimation) based on pulse transit time (PTT) is performed, it is necessary to appropriately calibrate the correspondence formula Eq between the pulse transit time and the blood pressure (in the above example, update the values of the coefficients α, β, and the like based on the actually measured pulse transit time and the blood pressure value). Here, according to the sphygmomanometer 1, the blood pressure measurement by the oscillometric method can be performed with the same apparatus, and the correspondence formula Eq can be calibrated based on the result, so that the convenience of the user can be enhanced. In addition, a rapid rise in blood pressure can be captured by the PTT method (blood pressure measurement based on pulse transit time) that can be continuously measured even though the precision is low, and with the rapid rise in blood pressure as a trigger, measurement by a more precise oscillometric method can be started.
(First Modification)
In the above examples, as illustrated in
Furthermore, as illustrated in
It should be noted that there are individual differences in the shape of the measurement site (wrist). A person with an almost flat measurement site can be measured with sufficiently high precision even without flexibility. Flexibility allows measurement with high precision regardless of the shape of the measurement site.
(Second Modification)
In the above examples, the dielectric layer 402 constituting the transmitting and receiving antenna group 40E is assumed to be made of polycarbonate, that is, a material having relatively poor flexibility. Therefore, as illustrated in
(Third Modification)
In addition, the dielectric layer 402 constituting the transmitting and receiving antenna group 40E may be at least partially made of a hygroscopic cloth. For example, in the dielectric layer 402 having a three-layer structure shown in
(Fourth Modification)
In the above examples, the case is described where all of the dielectric layers 402 constituting the transmitting and receiving antenna group 40E have a square pattern shape. However, the present invention is not limited thereto. For example, as shown in
According to this configuration, the user's winding around the left wrist 90 with the strip-shaped layer portion 402B-2 of the dielectric layer 402B mounts the transmitting and receiving antenna group 40E on the left wrist 90. That is, the strip-shaped layer portion 402B-2 can constitute a part of the belt 20 that winds around the left wrist 90 (for example, an inner cloth that covers the inner peripheral surface 20a of the belt 20). In addition, for example, in a case of a simple configuration where the pressing cuff 21 is omitted in the belt 20 and only blood pressure measurement based on the pulse transit time (PTT) is performed, the belt 20 can be entirely constituted by the strip-shaped layer portion 402B-2.
In this example, it is particularly desirable that the strip-shaped layer portion 402B-2 is made of a hygroscopic cloth. In that case, even if sweat of the living body occurs on the left wrist 90, the sweat is absorbed by the strip-shaped layer portion 402B-2 (made of hygroscopic cloth) of the dielectric layer 402B and is prevented from staying between the outer peripheral surface of the left wrist 90 and the inner peripheral surface of the strip-shaped layer portion 402B-2. As a result, discomfort of the user is reduced.
It should be noted that as in the dielectric layer 402C shown in
(Fifth Modification)
In the above examples, the case is described where the dielectric layer 402 constituting the transmitting and receiving antenna group 40E has a square pattern shape corresponding at least partially to the facing surface 401b of the conductor layers 401 and 401A. However, the present invention is not limited thereto. For example, in a case of a simple configuration where the pressing cuff 21 is omitted and only blood pressure measurement based on the pulse transit time (PTT) is performed, as shown in
(Sixth Modification)
In the above examples, the case is described where the relative permittivity of the portion corresponding to the facing surface 401b of the conductor layer of each of the dielectric layers 402, 402A, 402B, 402C, and 402D is uniform in the surface direction u. However, the present invention is not limited thereto. For example, a dielectric layer 402E as shown in
In this example, the area of the dielectric layer 402E in the surface direction u is set to 10 mm2, and the dimension in the thickness direction v is set to 2 mm. The area in the surface direction u of each through hole 402w is set to 2 mm2 (therefore, the diameter is about 0.5 mm). When the number of through holes 402w is, for example, 10, the effective relative permittivity as a whole of the dielectric layer 402E is εr≈2.6.
Varying the number of these through holes 402w, 402w, . . . or the density in the surface direction u allows the effective relative permittivity as a whole of the dielectric layer 402E to be variably set. Therefore, the degree of freedom for setting the effective relative permittivity as a whole of the dielectric layer 402E is increased.
It should be noted that in order to variably set the effective relative permittivity as a whole of the dielectric layer 402, a plurality of minute spherical cavities may be provided inside the dielectric layer 402 in a dispersed manner in the surface direction u and the thickness direction v, for example.
(Effect of Interposing Dielectric Layer)
(Seventh Modification)
In each of the above examples, a case is described in which the dielectric layer is directly mounted along the facing surface (the surface facing the left wrist 90) 401b of the conductor layer 401 or 401A constituting the transmitting and receiving antenna group 40E. However, the present invention is not limited thereto. For example, as shown in
In this configuration, in the mounted state where the transmitting and receiving antenna group 40E is mounted on the left wrist 90, the conductor layer 401 is disposed facing the palmar surface 90a of the left wrist 90, and the dielectric layer 402F is disposed between the palmar surface 90a of the left wrist 90 and the facing surface 400b of the base material 400. A gap d2 is formed between a portion 90a1 corresponding to the radial artery 91 of the palmar surface 90a of the left wrist 90 and the facing surface 401b of the conductor layer 401. In this mounted state, the dielectric layer 402F keeps the distance (distance in the thickness direction v) between the palmar surface 90a of the left wrist 90 and (the facing surface 401b of) the conductor layer 401 constant.
In this mounted state, a radio wave is emitted from the transmitting antenna 41 toward the left wrist 90 through the gap d2 (or the dielectric layers 402F present on the sides of the gap d2). The radio wave reflected by the left wrist 90 is received by the receiving antenna 42 through the gap d2 (or the dielectric layers 402F present on the sides of the gap d2). Here, according to this configuration, since the dielectric layer 402F keeps the distance between the palmar surface 90a of the left wrist 90 and the conductor layer 401 (transmitting and receiving antenna pair (41, 42)) constant, the received signal level is stabilized, and biological information can be measured with high precision. In addition, as compared with the above examples, dielectric loss due to the dielectric layer immediately below the conductor layer 401 can be reduced, and the SN ratio of the received signal can be increased. Therefore, the pulse wave signals PS1 and PS2 as biological information can be measured with high precision.
In the above-described embodiment, as shown in
In the above-described embodiment, it is assumed that the conductor layers 401 and 401A are configured such that the transmitting antenna and the receiving antenna that receives a radio wave from the transmitting antenna are separated from each other and divided. However, the present invention is not limited thereto. The conductor layer forming the biometric antenna device may be used as a spatially single transmitting and receiving shared antenna via a known circulator for the emission and reception of radio waves.
In addition, in the above embodiment, the sphygmomanometer 1 is intended to be mounted on the left wrist 90 as a measurement site. However, the present invention is not limited thereto. The measurement site has only to be a site which an artery passes through, may be the right wrist, an upper limb such as an upper arm other than the wrist, and may be a lower limb such as an ankle or thigh.
In addition, in the above embodiments, the CPU 100 mounted on the sphygmomanometer 1 is assumed to work as a pulse wave detection unit, and first and second blood pressure calculation units to perform blood pressure measurement by oscillometric method (operation flow in
In the above-described embodiments, the sphygmomanometer 1 measures the pulse wave signal, the pulse transit time, and the blood pressure as biological information, but the present invention is not limited thereto. Various other pieces of biological information such as the pulse rate may be measured.
In addition, the present invention may constitute an apparatus including a biometric antenna device, a pulse wave measurement device, or a blood pressure measurement device and further including a functional unit for performing another function. According to this apparatus, biological information can be measured with high precision, and in particular, pulse wave signals can be acquired with high precision as biological information, or the blood pressure value can be calculated (estimated) with high precision. In addition, this apparatus can perform various functions.
As described above, a biometric antenna device of the present disclosure for emitting a radio wave toward a measurement site of a living body or for receiving a radio wave from the measurement site, the biometric antenna device comprises:
a conductor layer configured to face the measurement site for emitting and/or receiving the radio wave; and
a dielectric layer mounted along a facing surface facing the measurement site of the conductor layer or of a base material mounting the conductor layer and extending in parallel with the conductor layer, the dielectric layer having a predetermined relative permittivity,
wherein the dielectric layer keeps a distance between an outer surface of the measurement site and the conductor layer constant, in a mounted state in which a second surface on a side opposite to a side of a first surface on a side along the conductor layer of the dielectric layer abuts on an outer surface of the measurement site.
In the present specification, the “measurement site” may be a trunk in addition to a rod-shaped site such as an upper limb (wrist, upper arm, or the like) or a lower limb (ankle, or the like).
In addition, the “outer surface” of the measurement site refers to a surface exposed to the outside. For example, if the measurement site is a wrist, it refers to the outer peripheral surface of the wrist or a part thereof (for example, the palmar surface corresponding to the palmar side portion in the circumferential direction of the outer peripheral surface).
In addition, the “conductor layer” can be used, for emitting and/or receiving a radio wave, as a transmitting antenna or a receiving antenna, or as a transmitting and receiving shared antenna via a known circulator. The “conductor layer” may be divided into a transmitting antenna and a receiving antenna that receives a radio wave from the transmitting antenna.
In addition, unless otherwise noted, the “predetermined relative permittivity” of the dielectric layer may be uniform over the range in which the dielectric layer occupies space, or may vary depending on the position within a range in which the dielectric layer occupies space.
In addition, a phrase that the dielectric layer “keeps a distance constant” between an outer surface of the measurement site and the conductor layer means that the dielectric layer is a spacer. It should be noted that in the case where the dielectric layer has flexibility, it means acceptable that the “distance” more or less fluctuates due to the bending when it is bent by an external force.
In the biometric antenna device of the present invention, in the mounted state mounted on the measurement site, a second surface of the dielectric layer on a side opposite to a side of the first surface on a side along the conductor layer abuts on the outer surface of the measurement site. In this mounted state, the conductor layer faces the outer surface of the measurement site, and the dielectric layer keeps a distance between the outer surface of the measurement site and the conductor layer (distance in the thickness direction) constant. When the conductor layer is used as a transmitting antenna in this mounted state, a radio wave is emitted from the conductor layer toward the measurement site through the dielectric layer (or a gap present on the side of the dielectric layer). Here, since the dielectric layer keeps the distance between the outer surface of the measurement site and the conductor layer constant, the signal level applied to the measurement site is stabilized. On the other hand, when the conductor layer is used as a receiving antenna, the radio wave reflected by the measurement site is received by the conductor layer through the dielectric layer (or a gap present on the side of the dielectric layer). Here, the dielectric layer keeps the distance between the outer surface of the measurement site and the conductor layer constant. In addition, due to the dielectric layer interposed between the outer surface of the measurement site and the conductor layer (or the base material), it is less likely to be affected by fluctuations in the dielectric constant of the living body (the relative permittivity of the living body varies in the range of about 5 to 40). In addition, since room between the outer surface of the measurement site and the conductor layer can be made, the range (area) of the measurement site irradiated with a radio wave can be expanded as compared with the case where the conductor layer is in direct contact with the outer surface of the measurement site. As a result, the received signal level is stabilized. Therefore, according to this biometric antenna device, biological information can be measured with high precision.
In the biometric antenna device of one embodiment, the conductor layer or the base material and the dielectric layer have flexibility configured to be deformed along an outer surface of the measurement site as a whole.
When the biometric antenna device of this embodiment is mounted on the measurement site of the living body, the conductor layer or the base material and the dielectric layer can be deformed along the outer surface of the measurement site as a whole due to the flexibility. Therefore, even when the outer surface of the measurement site is curved, a gap is unlikely to occur between the outer surface of the measurement site and the second surface of the dielectric layer. As a result, even when the outer surface of the measurement site is curved, the distance between the outer surface of the measurement site and the conductor layer is kept constant. In addition, power reflection at the interface between the measurement site and the dielectric layer is reduced. In addition, since no gap occurs between the outer surface of the measurement site and the second surface of the dielectric layer, no radio wave propagation loss due to such a gap occurs. Therefore, the received signal level is further stabilized, and the biological information can be measured with high precision.
In the biometric antenna device of one embodiment, a relative permittivity of the dielectric layer at a frequency of the radio wave is set within a range of 1 to 5.
Here, the relative permittivity εr=1 corresponds to the relative permittivity of air. The relative permittivity εr=5 corresponds to the lower limit of the relative permittivity of the living body (measurement site) because the relative permittivity of the living body is in the range of about 5 to 40.
In the biometric antenna device of this embodiment, the relative permittivity (εr) of the dielectric layer at the frequency of the radio wave is set within a range of 1 to 5. Therefore, the relative permittivity (εr) of the dielectric layer and the relative permittivity of the measurement site increase in this order. Therefore, power reflection at the interface between the measurement site and the dielectric layer is reduced. As a result, the signal-to-noise ratio of the received signal is increased, and biological information can be measured with high precision.
In the biometric antenna device of one embodiment, a relative permittivity of the dielectric layer at a frequency of the radio wave is gradually increased from the first surface toward the second surface.
In the biometric antenna device of this embodiment, the relative permittivity (εr) of the dielectric layer at the frequency of the radio wave gradually increases from the first surface (the surface on the side along the conductor layer) toward the second surface (the surface on the side abutting on the measurement site in the mounted state). Therefore, power reflection at the interface between the measurement site and the dielectric layer is reduced. As a result, the SN ratio (signal-to-noise ratio) of the received signal is increased, and biological information can be measured with high precision.
In the biometric antenna device of one embodiment, the dielectric layer has a plurality of cavities dispersed inside the dielectric layer, and therefore, an effective relative permittivity as a whole of the dielectric layer is set lower than a relative permittivity of a material itself of the dielectric layer.
In the biometric antenna device of this embodiment, the dielectric layer has a plurality of cavities dispersed inside the dielectric layer. The relative permittivity of the cavity is approximately equal to 1, and is smaller than the relative permittivity of the material itself of the dielectric layer. Thus, the effective relative permittivity as a whole of the dielectric layer is set lower than the relative permittivity of the material itself of the dielectric layer. Therefore, the degree of freedom for setting the effective relative permittivity as a whole of the dielectric layer is increased.
In the biometric antenna device of one embodiment, the dielectric layer includes a specific portion provided in a range corresponding to the facing surface of the conductor layer or the base material, and a strip-shaped layer portion extending in a strip shape beyond a range occupied by the specific portion, and is constituted to stack the specific portion and the strip-shaped layer portion in a thickness direction.
Here, the “thickness direction” means a direction perpendicular to a direction in which the conductor layer or the dielectric layer spreads in a layer shape (referred to as a “surface direction”).
The biometric antenna device of this embodiment can be mounted on the measurement site in a mode where the strip-shaped layer portion of the dielectric layer winds around the measurement site. Thus, this biometric antenna device is stably mounted on the measurement site.
In addition, in particular, when the strip-shaped layer portion is made of a hygroscopic cloth, even if sweat of the living body occurs in the measurement site, the sweat is absorbed by the strip-shaped layer portion (made of a hygroscopic cloth) of the dielectric layer and is prevented from staying between the outer surface of the measurement site and the second surface of the dielectric layer. As a result, the discomfort of the living body (subject) mounting the biometric antenna device is reduced.
It should be noted that the “strip-shaped layer portion” may constitute a part or a whole of the belt mounted to wind around the measurement site.
In the biometric antenna device of one embodiment, the biometric antenna device further comprises a belt mounted to wind around the measurement site,
wherein the belt is mounted with the conductor layer or the base material and the dielectric layer.
The user's (including a subject. The same applies hereinafter.) winding the belt around the measurement site mounts the biometric antenna device of this embodiment on the measurement site. Thus, this biometric antenna device is stably mounted on the measurement site. In the mounted state, a second surface of the dielectric layer on a side opposite to a side of the first surface on a side along the conductor layer abuts on the outer surface of the measurement site. Then, the dielectric layer keeps the distance (distance in the thickness direction) between the outer surface of the measurement site and the conductor layer constant. Therefore, the received signal level is stabilized, and the biological information can be measured with high precision.
In the biometric antenna device of one embodiment, the dielectric layer includes only a portion corresponding to the facing surface of the conductor layer or the base material, of the belt.
In the biometric antenna device of this embodiment, the dielectric layer includes only a portion corresponding to the facing surface of the conductor layer or the base material, of the belt. Therefore, the configuration of the dielectric layer can be simplified.
In another aspect, a pulse wave measurement device of the present disclosure for measuring a pulse wave of a measurement site of a living body, the pulse wave measurement device comprises:
the biometric antenna device;
wherein the second surface of the dielectric layer is configured to abut on an outer surface of the measurement site, and a transmitting and receiving antenna pair including a transmitting antenna and a receiving antenna formed by the conductor layer is configured to correspond to an artery passing through the measurement site in a mounted state in which the belt is mounted to wind around an outer surface of the measurement site,
a transmitting circuit configured to emit a radio wave toward the measurement site via the transmitting antenna;
a receiving circuit configured to receive a radio wave reflected by the measurement site via the receiving antenna; and
a pulse wave detection unit configured to acquire a pulse wave signal representing a pulse wave of an artery passing through the measurement site based on an output of the receiving circuit.
Here, when the conductor layer is divided into a transmitting antenna and a receiving antenna that receives a radio wave from the transmitting antenna in the surface direction perpendicular to the thickness direction of the conductor layer, the “transmitting and receiving antenna pair” refers to the transmitting antenna and the receiving antenna. In addition, when the conductor layer spatially forms one transmitting and receiving shared antenna, all of the “transmitting antenna”, the “receiving antenna”, and the “transmitting and receiving antenna pair” refer to the transmitting and receiving shared antenna.
The user's winding the belt around the outer surface of the measurement site mounts the pulse wave measurement device of the present disclosure on the measurement site. In the mounted state, the second surface of the dielectric layer abuts on the outer surface of the measurement site. Therefore, the conductor layer faces the outer surface of the measurement site, and the dielectric layer keeps a distance between the outer surface of the measurement site and the conductor layer constant. In addition, a transmitting and receiving antenna pair including a transmitting antenna and a receiving antenna formed by the conductor layer corresponds to an artery passing through the measurement site. In this mounted state, the transmitting circuit emits a radio wave toward the measurement site via the transmitting antenna, that is, from the conductor layer through the dielectric layer (or a gap present on the side of the dielectric layer). In addition, the receiving circuit receives a radio wave reflected by the measurement site with the conductor layer via the receiving antenna, that is, through the dielectric layer (or a gap present on the side of the dielectric layer). The pulse wave detection unit acquires a pulse wave signal representing the pulse wave of the artery passing through the measurement site based on the output of the receiving circuit.
Here, in the mounted state, since the dielectric layer keeps a distance between the outer surface of the measurement site and the conductor layer (which forms the transmitting and receiving antenna pair) constant, the received signal level is stabilized. In particular, since the room between the outer surface of the measurement site and the conductor layer can be made, the range (area) of the measurement site irradiated with a radio wave can be expanded. Therefore, even if the mounting position of the conductor layer is more or less deviated from directly above the radial artery, the signal reflected by the radial artery can be stably received. Therefore, the pulse wave detection unit can acquire a pulse wave signal as biological information with high precision.
In another aspect, a blood pressure measurement device of the present disclosure for measuring blood pressure of a measurement site of a living body, the blood pressure measurement device comprises:
the two sets of pulse wave measurement devices;
wherein a belt in the two sets is integrally formed,
wherein transmitting and receiving antenna pairs in the two sets are arranged apart from each other in a width direction of the belt,
wherein in a mounted state where the belt is mounted to wind around an outer surface of the measurement site, the second surface of the dielectric layer abuts on an outer surface of the measurement site, and a first set of transmitting and receiving antenna pair of the two sets corresponds to an upstream side portion of an artery passing through the measurement site, while a second set of transmitting and receiving antenna pair corresponds to a downstream side portion of the artery,
wherein in each of the two sets, the transmitting circuit emits a radio wave toward the measurement site via the transmitting antenna, and the receiving circuit receives a radio wave reflected by the measurement site via the receiving antenna, and
wherein in each of the two sets, the pulse wave detection unit acquires a pulse wave signal representing a pulse wave of an artery passing through the measurement site based on an output of the receiving circuit,
a time difference acquisition unit configured to acquire a time difference between pulse wave signals acquired by the two sets of respective pulse wave detection units as a pulse transit time; and
a first blood pressure calculation unit configured to calculate a blood pressure value based on a pulse transit time acquired by the time difference acquisition unit by using a predetermined correspondence formula between a pulse transit time and a blood pressure.
In the blood pressure measurement device of the present disclosure, the belt in the two sets is integrally formed, and the transmitting and receiving antenna pairs in the two sets are arranged apart from each other in the width direction of the belt. In the mounted state in which the belt is mounted to wind around the outer surface of the measurement site, in each of the two sets, the second surface of the dielectric layer abuts on the outer surface of the measurement site. Therefore, the conductor layer faces the measurement site, and the dielectric layer keeps a distance between the outer surface of the measurement site and the conductor layer constant. In addition, the first set of transmitting and receiving antenna pair of the two sets corresponds to the upstream side portion of the artery passing through the measurement site, while the second set of transmitting and receiving antenna pair corresponds to the downstream side portion of the artery. In this mounted state, in each of the two sets, the transmitting circuit emits a radio wave toward the measurement site via the transmitting antenna, and the receiving circuit receives a radio wave reflected by the measurement site via the receiving antenna. Specifically, in the first set, the transmitting circuit emits a radio wave toward the upstream side portion of the artery via the transmitting antenna, that is, from the conductor layer through the dielectric layer (or a gap present on the side of the dielectric layer). Along with this, the receiving circuit receives a radio wave reflected by the upstream side portion with the conductor layer via the receiving antenna, that is, through the dielectric layer (or a gap present on the side of the dielectric layer). In addition, in the second set, the transmitting circuit emits a radio wave toward the downstream side portion of the artery via the transmitting antenna, that is, from the conductor layer through the dielectric layer (or a gap present on the side of the dielectric layer). Along with this, the receiving circuit receives a radio wave reflected by the downstream side portion with the conductor layer via the receiving antenna, that is, through the dielectric layer (or a gap present on the side of the dielectric layer). Next, in each of the two sets, the pulse wave detection unit acquires a pulse wave signal representing the pulse wave of the artery passing through the measurement site based on the output of the receiving circuit. Specifically, in the first set, the pulse wave detection unit acquires a pulse wave signal representing the pulse wave of the artery passing through the upstream side portion of the artery based on the output of the receiving circuit. In addition, in the second set, the pulse wave detection unit acquires a pulse wave signal representing the pulse wave of the artery passing through the downstream side portion of the artery based on the output of the receiving circuit. Next, the time difference acquisition unit acquires a time difference between the pulse wave signals acquired by the respective two sets of pulse wave detection units as a pulse transit time. Thereafter, the first blood pressure calculation unit calculates a blood pressure value based on the pulse transit time acquired by the time difference acquisition unit by using a predetermined correspondence formula between the pulse transit time and the blood pressure.
Here, in the blood pressure measurement device, in the mounted state, in each of the two sets, the dielectric layer keeps a distance between the outer surface of the measurement site and the conductor layer (which forms the transmitting and receiving antenna pair) constant. Therefore, in each of the two sets, the received signal level is stable and the pulse wave detection unit can acquire a pulse wave signal as biological information with high precision. As a result, the time difference acquisition unit can acquire the pulse transit time with high precision, and thus the first blood pressure calculation unit can calculate (estimate) the blood pressure value with high precision.
In the blood pressure measurement device of one embodiment, the belt is mounted with a fluid bag for pressing the measurement site, further comprising:
a pressure control unit configured to supply air to the fluid bag to control pressure; and
a second blood pressure calculation unit configured to calculate blood pressure by an oscillometric method based on pressure in the fluid bag.
In the blood pressure measurement device of this embodiment, the blood pressure measurement (estimation) based on the pulse transit time and the blood pressure measurement by the oscillometric method can be performed by using a common belt. Therefore, the convenience of the user is enhanced.
In another aspect, an apparatus of the present disclosure comprises:
the biometric antenna device;
the pulse wave measurement device; or
the blood pressure measurement device.
An apparatus of the present disclosure may include the biometric antenna device, the pulse wave measurement device, or the blood pressure measurement device and may include a functional unit for performing another function. According to this apparatus, biological information can be measured with high precision, pulse wave signals as biological information can be acquired with high precision, or the blood pressure value can be calculated (estimated) with high precision. In addition, this apparatus can perform various functions.
In another aspect, a biological information measurement method of the present disclosure for acquiring biological information from a measurement site of a living body by using the biometric antenna device, the biological information measurement method comprises:
causing the second surface of the dielectric layer to abut on an outer surface of the measurement site to mount the biometric antenna device on the measurement site; and
in a mounted state where the dielectric layer keeps a distance between an outer surface of the measurement site and the conductor layer constant, emitting a radio wave from the conductor layer toward the measurement site through the dielectric layer or a gap present on a side of the dielectric layer, and/or receiving a radio wave reflected by the measurement site with the conductor layer through the dielectric layer or a gap present on a side of the dielectric layer.
According to the biological information measurement method of the present disclosure, in the mounted state, the dielectric layer keeps the distance between the outer surface of the measurement site and the conductor layer constant. In addition, due to the dielectric layer interposed between the outer surface of the measurement site and the conductor layer (or the base material), it is less likely to be affected by fluctuations in the dielectric constant of the living body (the relative permittivity of the living body varies in the range of about 5 to 40). In addition, since room between the outer surface of the measurement site and the conductor layer can be made, the range (area) of the measurement site irradiated with a radio wave can be expanded as compared with the case where the conductor layer is in direct contact with the outer surface of the measurement site. As a result, the received signal level is stabilized. Therefore, according to this biometric antenna device, biological information can be measured with high precision.
In another aspect, a pulse wave measurement method of the present disclosure for measuring a pulse wave of a measurement site of a living body by using the pulse wave measurement device, the pulse wave measurement method comprises:
mounting the belt to wind around an outer surface of the measurement site, causing the second surface of the dielectric layer to abut on an outer surface of the measurement site, and causing a transmitting and receiving antenna pair including a transmitting antenna and a receiving antenna formed by the conductor layer to correspond to an artery passing through the measurement site;
in a mounted state in which the dielectric layer keeps a distance between the measurement site and the conductor layer constant, emitting a radio wave toward the measurement site with the transmitting circuit via the transmitting antenna, and receiving a radio wave reflected by the measurement site with the receiving circuit via the receiving antenna; and
acquiring a pulse wave signal representing a pulse wave of an artery passing through the measurement site with the pulse wave detecting unit based on an output of the receiving circuit.
According to the pulse wave measurement method of the present disclosure, in the mounted state, since the dielectric layer keeps a distance between the outer surface of the measurement site and the conductor layer (which forms the transmitting and receiving antenna pair) constant, the received signal level is stabilized. In particular, since the room between the outer surface of the measurement site and the conductor layer can be made, the range (area) of the measurement site irradiated with a radio wave can be expanded. Therefore, even if the mounting position of the conductor layer is more or less deviated from directly above the radial artery, the signal reflected by the radial artery can be stably received. Therefore, the pulse wave signal as biological information can be acquired with high precision.
In another aspect, a blood pressure measurement method of the present disclosure for measuring blood pressure of a measurement site of a living body by using the blood pressure measurement device, the blood pressure measurement method comprises:
mounting the belt to wind around an outer surface of the measurement site, causing the second surface of the dielectric layer to abut on an outer surface of the measurement site, and causing a first set of transmitting and receiving antenna pair of the two sets to correspond to an upstream side portion of an artery passing through the measurement site, while causing a second set of transmitting and receiving antenna pair to correspond to a downstream side portion of the artery;
in a mounted state where the dielectric layer keeps a distance between the measurement site and the conductor layer constant, in each of the two sets, emitting a radio wave toward the measurement site with the transmitting circuit via the transmitting antenna, and receiving a radio wave reflected by the measurement site with the receiving circuit via the receiving antenna;
in each of the two sets, acquiring a pulse wave signal representing a pulse wave of an artery passing through the measurement site with the pulse wave detection unit based on an output of the receiving circuit;
acquiring a time difference between pulse wave signals acquired by the two sets of respective pulse wave detection units with the time difference acquisition unit as a pulse transit time; and
calculating a blood pressure value with the first blood pressure calculation unit based on a pulse transit time acquired by the time difference acquisition unit by using a predetermined correspondence formula between a pulse transit time and a blood pressure.
According to this blood pressure measurement method, in the mounted state, in each of the two sets, the dielectric layer keeps a distance between the outer surface of the measurement site and the conductor layer (which forms the transmitting and receiving antenna pair) constant. Therefore, in each of the two sets, the received signal level is stable and the pulse wave signal as biological information can be acquired with high precision. As a result, the pulse transit time can be acquired with high precision, and therefore, the blood pressure value can be calculated (estimated) with high precision.
The above embodiments are illustrative, and various modifications can be made without departing from the scope of the present invention. It is to be noted that the various embodiments described above can be appreciated individually within each embodiment, but the embodiments can be combined together. It is also to be noted that the various features in different embodiments can be appreciated individually by its own, but the features in different embodiments can be combined.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-142231 | Jul 2017 | JP | national |
This is a continuation application of International Application No. PCT/JP2018/024043, with an International filing date of Jun. 25, 2018, which claims priority of Japanese Patent Application No. 2017-142231 filed on Jul. 21, 2017, the entire content of which is hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2018/024043 | Jun 2018 | US |
| Child | 16736515 | US |
